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  • 1.
    Jacobsson, Linn
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Regulation and function of Pax-6 during head and eye development in Drosophila melanogaster2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In Drosophila melanogaster, eyeless and twin of eyeless have important function during eye development. Mutants of both genes give a variety of eye and head phenotypes with the strongest being almost headless meaning that they lack all structures derived from the eye-antennal disc. toy the first eye specification gene expressed in the regulatory network that leads to eye formation and the gene actvates eyeless. What regulates toy is still not clear and has been the focus of this thesis. In Paper I, we analysed part of the upstream region of the toy gene to be able to drive reporter genes with the expected expression pattern in embyo and larval tissues. We found that a 1300-bp region surrounding the toy transcription start is important for correct Toy expression during embryonic and larval development. We also tested for possible redundancy between the toy and ey genes by rescue experiments on some lethal allels in both genes and found that Pax-6 proteins can substitute for each other concerning both head structures and survival. However, rescue is only partial, indicating that the proteins are not fully compatible or that the levels of expression are not sufficiently reproduced by the artificial Gal4-UAS system. Furthermore, we show that inhibition of apoptosis increased survival in strong toy mutants, but did not improve eye phenotypes. In Paper II, we searched for possibly upstream regulators of toy and found that the head gap gene empty spiracles changed the expression pattern of Toy significantly in the embryonic eye-antennal primordium. By clonal analysis and ectopic expressions, we made the conclusion that Ems acts as a repressor of toy during late embryonic development and also at later developmental stages. In Paper III, we investigate presumptive toy enhancer regions within the intron sequences of the gene. Generation and examination of transgenic lines showed that there might be an enhancer region driving toy expression in the embryonic ventral nerve cord within intron 2.

    Ladda ner fulltext (pdf)
    Regulation and function of Pax-6 during head and eye development in Drosophila melanogaster
  • 2.
    Jacobsson, Linn
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Kronhamn, Jesper
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Rasmuson-Lestander, Åsa
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    The Drosophila Pax6 paralogs have different functions in head development but can partially substitute for each other2009Ingår i: Molecular Genetics and Genomics, ISSN 1617-4615, E-ISSN 1617-4623, Vol. 282, nr 3, s. 217-231Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There are two Pax6 genes in Drosophila melanogaster; eyeless (ey) and twin-of-eyeless (toy), due to a duplication, which most likely occurred in the insect lineage. They encode transcription factors important for head development. Misexpression of either toy or ey can induce formation of ectopic compound eyes. Toy regulates the ey gene by binding to an eye-specific enhancer in its second intron. However, Toy can induce ectopic eyes also in an ey( - ) background, which indicates a redundancy between the two Pax6 copies in eye formation. To elucidate to what extent these two genes are interchangeable, we first generated toy-Gal4 constructs capable of driving the Pax6 genes in a toy-specific manner. Genetic dissection of the promoter proximal region of toy identified a 1,300-bp region around the canonical transcription start that is sufficient to drive toy expression in embryonic brain and eye primorida and in larval eye-antennal discs. We find that exogenous expression of toy can partially rescue the lethality and eye phenotype caused by lethal mutations in ey and vice versa. We therefore conclude that Toy and Ey, to some extent, can substitute for each other. Nevertheless, the phenotypes of the rescued flies indicate that the two Pax6 genes are specialized to regulate defined structures of the fly head.

  • 3.
    Jacobsson, Linn
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Rasmuson-Lestander, Åsa
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Identification of regulatory regions within the intron sequence of the toy geneManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In Drosophila there are two paralougus Pax-6 genes, twin of eyeless (toy) and eyeless (ey) Both genes have an extensive elaborate expression pattern in the brain and ventral nerve cord but are not activated at the same time in these regions. Since both genes are expressed in several tissues during different time points in development, one might expect that more than one regulatory enhancer controls them. It is known, that eyeless is directly regulated by toy at the beginning of eye development and it has been shown that there are binding sites for regulatory proteins within the introns of the eyeless gene and in vertebrate Pax-6 genes. We investigate the transcriptional activation of toy within the intron sequences of the gene and show that there is a presumptive regulatory element in intron 2, controlling toy expression in the ventral nerve cord of embryos.

  • 4.
    Jacobsson, Linn
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Skottheim Honn, John
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Ekström, Karin
    Rasmuson-Lestander, Åsa
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Empty spiracles represses twin-of-eyeless in the Drosophila embryonic headManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The specification of the eye-antennal disc primordium in the Drosophila embryo requires the expression of two paralogous Pax6 genes: twin of eyeless (toy) and eyeless (ey). toy is considered to be the first eye specification gene expressed in the regulatory network that governs eye formation and the gene that, in turn, activates eyeless. What regulates toy expression is, however, still unclear. We show, by misexpression and mutant analysis, that the head-specific gene empty spiracles alters the expression pattern of Toy in the head region around the visual primordia.

  • 5.
    Skottheim Honn, John
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Johansson, Linn
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Rasmuson Lestander, Asa
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Regulation of twin of eyeless during Drosophila development2016Ingår i: Gene Expression Patterns, ISSN 1567-133X, E-ISSN 1872-7298, Vol. 20, nr 2, s. 120-129Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Pax-6 protein is vital for eye development in all seeing animals, from sea urchins to humans. Either of the Pax6 genes in Drosophila (twin of eyeless and eyeless) can induce a gene cascade leading to formation of entire eyes when expressed ectopically. The twin of eyeless (toy) gene in Drosophila is expressed in the anterior region of the early fly embryo. At later stages it is expressed in the brain, ventral nerve cord and (eventually) the visual primordium that gives rise to the eye-antennal imaginal discs of the larvae. These discs subsequently form the major part of the adult head, including compound eyes. We have searched for genes that are required for normal toy expression in the early embryo to elucidate initiating events of eye organogenesis. Candidate genes identified by mutation analyses were subjected to further knock-out and miss-expression tests to investigate their interactions with toy. Our results indicate that the head-specific gap gene empty spiracles can act as a repressor of Toy, while ocelliless (oc) and spalt major (salm) appear to act as positive regulators of toy gene expression. (C) 2016 Elsevier B.V. All rights reserved.

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